Which advisor's missions unlock additional deployment slots?

I've been playing for a bit now, Necron Awakening level is at 40%, and thanks to Khepra I've got two additional Techpriests deployed.

The only problem is I still only have six deployment slots in the lander, which means that if I take all my priests I only have room for two cannon fodderSkitaari assistants, but on the mission prep screen there's another six (locked) deployment slots.

Presumably, one advisor or another gives out missions that will unlock those somewhere down their quest line, but which one?